Aqueous-based composition suitable for use in threadlocking applications

ABSTRACT

The present invention relates to aqueous-based compositions suitable for use in threadlocking applications comprising: a) at least one carboxyl group containing (co)polymer; b) at least one polymerizable monomer A containing one acryloyl group; c) at least one polymerizable compound B containing at least two acryloyl groups; d) at least one encapsulated free radical initiator; and e) water. The inventive aqueous-based compositions are preferably substantially free of volatile organic solvents.

FIELD OF THE INVENTION

The present invention relates to aqueous-based compositions suitable foruse in threadlocking applications comprising: a) at least one carboxylgroup containing (co)polymer; b) at least one polymerizable monomer Acontaining one acryloyl group; c) at least one polymerizable compound Bcontaining at least two acryloyl groups; d) at least one encapsulatedfree radical initiator; and e) water. Significantly, the inventiveaqueous-based compositions are preferably substantially free of volatileorganic solvents.

The aqueous-based compositions of the invention may be used to seal orlock engineering parts, particularly interfitting parts such asfasteners, more particularly threaded fasteners such as nuts, bolts,screws, threaded nails and the like, or parts such as pipe joints whichmay be threaded or slip-fitted.

BRIEF DESCRIPTION OF RELATED TECHNOLOGY

Compositions which are suitable for use in threadlocking applicationsare known.

Such compositions find use in many applications. In general thecompositions are used to lock interengaging threads together. Thecomposition is generally placed on one or both of fasteners which havereciprocal interengaging screw threads.

When the parts are screwed together using the screw threads thecomposition acts to lock the threads in the desired interengagedposition.

In general the applications in which aqueous-based compositions of thepresent invention are used include any application where it is desiredto lock screwthreads together so that the components which are screwedtogether do not become disengaged unintentionally, for example becauseof vibrational or other forces. Such applications include use in theconstruction of automobiles etc.

Compositions have been used which must be applied at the time ofthreading one component into another as the compositions remainsubstantially liquid before cure.

Such compositions include anaerobically curable compositions.

A pre-applied composition is described in U.S. Pat. No. 4,059,136, wheretwo physically separated deposits are applied to the threaded part. Acover coating is then applied over the deposits.

European Patent No. 0 077 659 (Thompson) describes a pre-appliedpolymerisable fluid for sealing and locking engineering parts. Thecomposition has two mechanisms for curing and two curing reactions takeplace. The first mechanism is a UV light cure. An opacifier is dispersedin the fluid so that the fluid becomes substantially opaque toradiation. After the fluid is applied to the component it is exposed toUV radiation whereupon a coating is formed, creating a surface layerwhich is a dry, tack-free crust. The subcutaneous fluid is unaffected bythe radiation and remains in a generally liquid state. When thecomponent is threaded into another the surface layer breaks and thesecond polymerisation (such as a free radical addition polymerization)is initiated and the second cure reaction takes place. The secondpolymerization mechanism acts to lock the threads together.

In Thompson, only a skin is formed in the first polymerization and theremainder of the composition remains fluid below the skin. There is arisk therefore that during handling of the coated engineering parts theskin may be disrupted and the fluid composition may leak out.

European Patent No. 0 548 369 (Usami) describes a pre-applied adhesivecomposition for application to the threaded contact faces of a screwmember such as a screw. The composition comprises a photo-hardeningbinder in which a secondary curable composition is dispersed. Thesecondary curable composition includes microencapsulated reactivemonomer/activator/initiator.

WO2004/024841 A2 (Haller) describes curable compositions for applicationto a threaded article. The composition comprises a dispersion ofcomponents of a first cure mechanism comprising: (a) a (meth)acrylatefunctional monomer component; (b) a (meth)acrylate functional oligomercomponent; and (c) a photoinitiator component; and (ii) components of asecond cure mechanism comprising: (e) an amine component; and (f) anencapsulated epoxy resin component; together with (iii) a thickenercomponent. The photoinitiator component is suitable upon irradiation ofthe composition to achieve a first cure through the depth of thecomposition applied to a threaded article so that a binder matrix isformed with the components of the second cure mechanism dispersedthrough the matrix.

The aforementioned compositions of the state of the art all comprise asignificant amount of volatile organic compounds (VOC). Environmentaland regulatory issues have developed recently over the use of VOCs inthreadlocking compositions because repeated or chronic exposure to thesecompounds may cause health problems.

Therefore, it would be desirable to reduce the amount of volatileorganic compounds in threadlocking compositions without sacrificingother properties such as their threadlocking performance anduser-friendly applicability.

SUMMARY OF THE INVENTION

The present invention provides an aqueous-based composition suitable forsealing or coating threaded fasteners and for threadlocking reciprocallythreaded articles. The composition comprises a) at least one carboxylgroup containing (co)polymer; b) at least one polymerizable monomer Acontaining one acryloyl group; c) at least one polymerizable compound Bcontaining at least two acryloyl groups; d) at least one encapsulatedfree radical initiator; and e) water.

Significantly, the inventive aqueous-based compositions are preferablysubstantially free of volatile organic solvents.

The inventive aqueous-based composition is preferably used in amulti-step process. In a first step said composition is applied to atleast one part of a fastener. At temperatures from 15° C. to 120° C. theaqueous-based composition is dried whereupon a dry and non-tacky coatingis formed on surface of the fastener. In a second step the dry andnon-tacky coating is cured by engaging the thread of the coated fastenerwith reciprocal thread of a receiver to form a reciprocally threadedarticle, wherein the threads of the reciprocally threaded article arebonded together by the cured product of the aqueous-based composition ofthe present invention. The curing process is activated by rupture of themicrocapsules resulting in reaction of the polymerizable components ofthe aqueous-based composition with the free radical initiator, which isreleased from the microcapsules.

In this regard, the invention provides a coated fastener that isobtained by a process comprising the steps of:

-   -   a) providing a fastener, preferably a threaded fastener;    -   b) applying to at least one part of the fastener an        aqueous-based composition of the present invention;    -   c) drying the fastener at temperatures from 15° C. to 120° C. to        form a coated fastener.

Further objects of the present invention are reciprocally threadedarticles having their respective threads bonded together by the curedproduct of the aqueous-based composition of the present invention and amethod for sealing and threadlocking a reciprocally threaded article,wherein said method comprises the steps of:

-   -   a) applying to at least one part of a threaded fastener an        aqueous-based composition of the present invention;    -   b) drying the threaded fastener at temperatures from 15° C. to        120° C. to form a coated fastener;    -   c) engaging the thread of the coated fastener with reciprocal        thread of a receiver to form a reciprocally threaded article,        wherein the threads of the reciprocally threaded article are        bonded together by the cured product of an aqueous-based        composition of the present invention.

Another object of the present invention is the use of the inventiveaqueous-based composition for sealing or coating threaded fastenersand/or for threadlocking reciprocally threaded articles.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

In a particular aspect the present invention provides an aqueous-basedcomposition comprising:

-   -   a) at least one carboxyl group containing (co)polymer;    -   b) at least one polymerizable monomer A containing one acryloyl        group;    -   c) at least one polymerizable compound B containing at least two        acryloyl groups;    -   d) at least one encapsulated free radical initiator; and    -   e) water.

As used in the present invention the term “aqueous-based composition”refers to a composition that comprises at least 10 percent by weight ofwater, based on the total amount of the inventive composition. Theaqueous-based composition of the present invention can also compriseminor amounts of other solvents, such as water-miscible solvents likealcohols.

Nevertheless it is preferred that the aqueous-based composition of thepresent invention is substantially free or completely free of volatileorganic solvents, wherein the term “substantially free” refers to acomposition that comprises, based on the total amount of thecomposition, less than 1 percent by weight, preferably less than 0.5percent by weight, and more preferably less than 0.1 percent by weightof one or more volatile organic solvents.

The viscosity of the inventive aqueous-based composition is preferablyin the range of 30 mPas to 30000 mPas, more preferably in the range of300 mPas to 20000 mPas when measured by a cone and plate viscosmeter(shear rate 129 s⁻¹) at a temperature of 22° C.

The aqueous-based composition of the present invention can be stored foruse in either a one-part or a two-part format. When formulated as atwo-part composition, one part of the composition may comprisecomponents a), b) and c) and a second part will usually containcomponent d).

Due to the encapsulation of the free radical initiator, the inventiveaqueous-based composition can preferably be formulated as a one-partcomposition, which is easy to handle and exhibit high storage stability.

Component a)—Carboxyl Group Containing (Co)Polymer

The at least one carboxyl group containing (co)polymer is used as awater dispersible or water-soluble binder component in the aqueous-basedcomposition of the present invention.

The carboxyl group containing (co)polymers of the present invention aredesigned to either dissolve or swell when revitalized with a base. Suchdissolution or swelling brings the aqueous-based composition to thedesired viscosity. Complete neutralization is typically experienced atabout pH 8.0.

The preferred weight-average molecular weight of the at least onecarboxyl group containing (co)polymer is in the range of 1,000 g/mol to500,000 g/mol, and more preferably in the range of 3000 g/mol to 200,000g/mol, as determined by gel permeation chromatography (GPC) using apolystyrene standard. If the molecular weight of the carboxyl groupcontaining (co)polymer is less than 1,000 g/mol, the binding function ofthe (co)polymer can be significantly reduced.

Suitable carboxyl group containing (co)polymers include polymers havinga glass transition temperature of from −20° C. to 50° C., preferably offrom −10° C. to 40° C. The glass transition temperature may be measuredby differential scanning calorimetry (DSC).

As used in the present invention the term (co)polymer refers to ahomopolymer or copolymer.

A carboxyl group containing homopolymer can be obtained by polymerizinga carboxyl group containing ethylenically unsaturated monomer.

A carboxyl group containing copolymer can be obtained by copolymerizingat least one carboxyl group containing ethylenically unsaturated monomerand at least one ethylenically unsaturated monomer, which does notcontain any carboxyl group.

Mixtures of different carboxyl group-containing ethylenicallyunsaturated monomers and/or mixtures of different ethylenicallyunsaturated monomers, which do not contain any carboxyl group, can beused to obtain the carboxyl group containing copolymers of the presentinvention.

Examples of the carboxyl group containing ethylenically unsaturatedmonomers include: unsaturated monocarboxylic acids such as acrylic acid,methacrylic acid, crotonic acid, alpha-chloroacrylic acid, and cinnamicacid; unsaturated dicarboxylic acids (acid anhydrides) such as maleicacid, maleic acid anhydride, fumaric acid, itaconic acid, itaconic acidanhydride, citraconic acid, citraconic acid anhydride, and mesaconicacid; tri- or higher-valent unsaturated polyvalent carboxylic acids(acid anhydrides); mono(2-acryloyloxyethyl) esters ormono(2-acryloyloxyethyl) esters of a nonpolymerizable dicarboxylic acidsuch as mono(2-acryloyloxyethyl) succinate, mono(2-methacryloyloxyethyl)succinate, mono(2-acryloyloxyethyl) phthalate, andmono(2-methacryloyloxyethyl) phthalate; and ω-carboxypolycaprolactonemonoacrylate and ω-carboxypolycaprolactone monomethacrylate. Thesecarboxyl group-containing ethylenically unsaturated monomers can be usedsingly or in combination of two or more of them.

Examples of the ethylenically unsaturated monomer, which does notcontain any carboxyl group, include aromatic vinyl compounds such asstyrene, alpha-methylstyrene, o-vinyltoluene, m-vinyltoluene,p-vinyltoluene, p-chlorostyrene, o-methoxystyrene, m-methoxystyrene,p-methoxystyrene, indene, p-vinylbenzyl methyl ether, p-vinylbenzylglycidyl ether; and aliphatic conjugated dienes such as 1,3-butadiene,isoprene, and chloroprene. These ethylenically unsaturated monomers canbe used singly or in combination of two or more of them.

In particular it is desirable that the at least one carboxyl groupcontaining (co)polymer is a copolymer composed of from 10 to 99 molepercentage, preferably of from 20 to 95 mole percentage, and morepreferably of from 50 to 90 mole percentage of one or more carboxylgroup containing ethylenically unsaturated monomer(s), and of from 1 to90 mole, preferably of from 5 to 80 mole percentage, and more preferablyof from 10 to 50 mole percentage of one or more ethylenicallyunsaturated monomer(s) that do not contain any carboxyl group.

In a preferred embodiment of the present invention the aforementionedcarboxyl group containing ethylenically unsaturated monomer is selectedfrom acrylic acid, methacrylic acid, crotonic acid, itaconic acid,fumaric acid, maleic acid, and citraconic acid and the aforementionedethylenically unsaturated monomer, which does not contain any carboxylgroup, is selected from vinyl aromatic compounds, such as styrene.

The carboxyl group containing (co)polymer or mixtures of differentcarboxyl group containing (co)polymers may be used in an amount of 15 to40 percent by weight, preferably in an amount of 20 to 35 percent byweight, and more preferably in an amount of 25 to 30 percent by weight,based on the total amount of the aqueous-based composition of thepresent invention.

In another preferred embodiment of the present invention the at leastone carboxyl group containing (co)polymer is provided as anaqueous-based emulsion or dispersion. Preferably said aqueous-basedemulsion or dispersion comprises water as the only solvent and issubstantially free of volatile organic solvents. Based on the totalamount of the emulsion or dispersion, the solids content preferablyranges from 45 to 65 percent by weight, such as from 48 to 58 percent byweight.

Preferred aqueous-based emulsions or dispersions are selected fromacrylic emulsions, styrene/acrylic emulsions, or mixtures thereof.

Examples of acrylic emulsions include poly(alkyl methacrylate-alkylacrylate), poly(alkyl methacrylate-aryl acrylate), poly(arylmethacrylate-alkyl acrylate), poly(alkyl methacrylate-acrylic acid), andpoly(alkyl acrylate-acrylonitrile-acrylic acid). The emulsion maycontain a resin such as poly(methyl methacrylate-butadiene), poly(ethylmethacrylate-butadiene), poly(propyl methacrylate-butadiene), poly(butylmethacrylate-butadiene), poly(methyl acrylate-butadiene), poly(ethylacrylate-butadiene), poly(propyl acrylate-butadiene), poly(butylacrylate-butadiene), poly(methyl methacrylate-isoprene), poly(ethylmethacrylate-isoprene), poly(propyl methacrylate-isoprene), poly(butylmethacrylate-isoprene), poly(methyl acrylate-isoprene), poly(ethylacrylate-isoprene), poly(propyl acrylate-isoprene), poly(butylacrylate-isoprene) and the like.

Examples of styrene/acrylic emulsions include poly(styrene-alkylacrylate), poly(styrene-1,3-diene), poly(styrene-alkyl methacrylate),poly(styrene-alkyl acrylate-acrylic acid),poly(styrene-1,3-diene-acrylic acid), poly(styrene-alkylmethacrylate-acrylic acid), poly(styrene-alkylacrylate-acrylonitrile-acrylic acid), andpoly(styrene-1,3-diene-acrylonitrile-acrylic acid). The emulsion maycontain a resin such as poly(styrene-butadiene),poly(methylstyrene-butadiene), poly(styrene-isoprene),poly(methylstyrene-isoprene), poly(styrene-propyl acrylate),poly(styrene-butyl acrylate), poly(styrene-butadiene-acrylic acid),poly(styrene-butadiene-methacrylic acid),poly(styrene-butadiene-acrylonitrile-acrylic acid), poly(styrene-butylacrylate-acrylic acid), poly(styrene-butyl acrylate-methacrylic acid),poly(styrene-butyl acrylate-acrylononitrile), poly(styrene-butylacrylate-acrylononitrile-acrylic acid) and the like.

Examples of specific aqueous-based emulsions or dispersions suitable foruse herein include Acrysol ASE-60, ASE-75, and ASE-95NP, Acusol 810, andRhoplex 1-2074 available from Rohm & Haas, Co, Acronal S728, NX4533 andS888S from BASF, and NeoCryl A-1120, a product of DSM Neoresins.

Component b)—Polymerizable Monomer a Containing One Acryloyl Group

The aqueous-based composition of the present invention further comprisesat least one polymerizable monomer A containing one acryloyl group.

The term “acryloyl group” as used herein refers to a functional grouphaving the structure

wherein R^(a) and R^(b) are each independently selected from hydrogen orC₁₋₁₂ alkyl and wherein R^(a) and R^(b) may be disposed either cis ortrans about the carbon-carbon double bond. Preferably, R^(a) and R^(b)are each independently hydrogen or methyl.

The polymerizable monomer A of the present invention is preferablyselected from hydrophobic esters of acrylic and/or methacrylic acid.

The term “hydrophobic” as used in the present invention refers tocompounds that exhibit a water solubility of less than 1.0 g, preferablyless than 0.8 g, and more preferably less than 0.7 g in 100 g ofdeionized water (ASTM D1193-91, type IV) at 22° C. and pH 7.

The hydrophobic group of the hydrophobic esters of acrylic andmethacrylic acid may comprise, for example, an alkyl group, an aromaticgroup, a cycloalkyl group, an alkenyl group, an alkynyl group or apolyether group and may be linear or branched. In this case, thehydrophobic group is preferably an alkyl group with a length of C₅ toC_(H), preferably C₈ to C₂₆, more particularly C₉ to C₂₂, above all C₁₀to C₂₀ or a polyalkylene glycol, more particularly a polyethyleneglycol, a polypropylene glycol or a copolymer of oxyethylene andoxypropylene units with preferably 2 to 50 and more preferably 2 to 30recurring units, the terminal hydroxy group of the polyalkylene glycolpreferably being esterified or etherified, the ester linkage preferablybeing formed with an acid selected from a C₅₋₅₀ carboxylic acid, moreparticularly a C₈₋₂₆ carboxylic acid and most preferably a C₁₆₋₂₀carboxylic acid, and the ether linkage preferably being formed with aC₅₋₅₀ alcohol, more particularly a C₈₋₂₆ alcohol and most preferably aC₁₆₋₂₀ alcohol.

In a particular preferred embodiment the at least one polymerizablemonomer A is selected from acrylic esters of formula (I),

wherein R¹ represents hydrogen or C₁₋₁₂ alkyl and R² is selected fromlinear or branched C₅₋₅₀ alkyl, C₅₋₅₀ cycloalkyl, C₅₋₅₀ alkenyl, orC₅₋₅₀ alkynyl. Preferably R¹ represents hydrogen or methyl and R²represents C₁₀₋₂₀ alkyl groups or C₆₋₂₀ cycloalkyl groups.

Examples of specific suitable polymerizable monomers A for use hereininclude isobornyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate,cyclohexyl (meth)acrylate, t-butyl cyclohexyl (meth)acrylate and/ortrimethyl cyclohexyl (meth)acrylate and/or mixtures thereof. It will beunderstood that the suffix (meth)acryl-denotes either acryl- ormethacryl-.

The polymerizable monomer A or mixtures of different polymerizablemonomers A may be used in an amount of 2 to 10 percent by weight,preferably in an amount of 3 to 9 percent by weight, and more preferablyin an amount of 4 to 8 percent by weight, based on the total amount ofthe aqueous-based composition of the present invention.

By adding at least one polymerizable monomer A, like hydrophobic estersof (meth)acrylic acid, such as isobornyl (meth)acrylate,tetrahydrofurfuryl (meth)acrylate, cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate and/or trimethyl cyclohexyl (meth)acrylate, tothe aqueous-based composition of the present invention a dry andnon-tacky coating can be formed. Comparable compositions that do notcomprise at least one polymerizable monomer A, like hydrophobic estersof (meth)acrylic acid, normally lead to coatings that exhibit anunacceptable degree of tackiness.

Component c)—Polymerizable Compound B Containing at Least Two AcryloylGroups

The aqueous-based composition of the present invention further comprisesat least one polymerizable compound B containing at least two acryloylgroups, wherein the polymerizable compound B is preferably selected fromacryloyl-containing polyesters, acryloyl-containing polyurethanes,alkoxylated acryloyl compounds and mixtures or copolymers thereof.

Suitable acryloyl-containing polyesters are for example unsaturatedpolyester resins that are the polycondensation reaction product of oneor more dihydric alcohols and one or more ethylenically unsaturatedpolycarboxylic acids. By polycarboxylic acid is meant polycarboxylic ordicarboxylic acids or anhydrides, polycarboxylic or dicarboxylic acidhalides, and polycarboxylic or dicarboxylic esters. For example,suitable unsaturated polycarboxylic acids, and the correspondinganhydrides and the acid halides that contain polymerizablecarbon-to-carbon double bonds, may include maleic anhydride, maleicacid, and fumaric acid. A minor proportion of the unsaturated acid, upto about forty mole percent, may be replaced by dicarboxylic orpolycarboxylic acid that does not contain a polymerizablecarbon-to-carbon bond. Examples thereof include the acids (andcorresponding anhydrides and acid halides): orthophthalic, isophthalic,terephthalic, succinic, adipic, sebacic, methylsuccinic, and the like.

Dihydric alcohols that are useful in preparing the polyesters include,for example, 1,2-propane diol (hereinafter referred to as propyleneglycol), dipropylene glycol, diethylene glycol, 1,3-butanediol, ethyleneglycol, glycerol, and the like.

Examples of suitable acryloyl-containing polyesters are thepolycondensation products of (1) propylene glycol and maleic and/orfumaric acids; (2) 1,3-butanediol and maleic and/or fumaric acids; (3)combinations of ethylene and propylene glycols (approximately 50 molepercent or less of ethylene glycol) and maleic and/or fumaric acids; andmixtures comprising at least one of the foregoing acryloyl monomers.

The molecular weight of the acryloyl-containing polyesters may vary overa considerable range, but ordinarily useful polyesters have a numberaverage molecular weight of about 300 g/mol to about 5,000 g/mol, andmore preferably about 500 g/mol to about 4,000 g/mol.

Suitable acryloyl-containing polyurethanes include trifunctionalurethane (meth)acrylates, such as the trifunctional urethane(meth)acrylates sold by Sartomer Company under the product names CN 929,CN 945 A60, CN 945 B85, CN 959, CN 962, CN 964, CN 965, CN 968, CN 980,CN 981, CN 983, CN 984, CN 944 B85, CN 953 B70, CN 963 B80, CN 964B85,CN 966 B85, CN 981 B88, CN 982 B88, CN 983 B88, CN 985 B88, CN 961H81,CN 966H90, CN 982 P90, CN 963 A80, CN 964 A85, CN 965 A80, CN 966 A80,CN 981 A75, CN 982 A75, CN 980 M50, CN 961 E75, CN 963 E75, CN 963 E80,CN 964 E75, CN 982 E75, CN 963 J85, CN 966 J75, CN 966 180, CN 966 R60,and CN 964H90; hexafunctional urethane (meth)acrylates, such as thehexafunctional urethane (meth)acrylates sold by Sartomer Company underthe product name CN 975; and urethane (meth)acrylates such as theurethane(meth)acrylates sold by Sartomer Company under the product namesCN 972, CN 2901, CN 2902, CN 978, CN 999, CN 970H75, CN 973H85, CN 970A60, CN 971 A80, CN 973 A80, CN 977 C70, CN 970 E60, CN 973 J75, and CN1963; and the like; and mixtures comprising at least one of theforegoing acryloyl monomers.

Suitable alkoxylated acryloyl compounds include compounds of formula(II),

wherein R³ is a C₁-C₂₅₀ organic group having a valence of c; eachoccurrence of R⁴ to R⁷ is independently hydrogen, C₁-C₆ alkyl, or C₅-C₁₂aryl; each occurrence of b is independently 0 to about 20 with theproviso that at least one occurrence of b is at least 1; each occurrenceof R²⁸ is independently hydrogen or methyl; and c is 2 to 10.

Within the above-stated range of 1 to about 20, the number of repeatingalkoxy units, b, is preferably at least 2, more preferably at least 3.Also within this range, b is preferably up to about 15, more preferablyup to about 10.

Within the above-stated range of 1 to about 10, the number ofalkoxylated acrylate units, c, is preferably at least 2, more preferablyat least 3. Also within this range, c is preferably up to about 8, morepreferably up to about 6.

Suitable alkoxylated acryloyl compounds include, for example,(ethoxylated)₂₋₄₀ 1,6-hexanediol di(meth)acrylate, (propoxylated)₂₋₄₀1,6-hexanediol di(meth)acrylate, (ethoxylated)₂₋₄₀ 1,4-butanedioldi(meth)acrylate, (propoxylated)₂₋₄₀ 1,4-butanediol di(meth)acrylate,(ethoxylated)₂₋₄₀ 1,3-butanediol di(meth)acrylate, (propoxylated)₂₋₄₀1,3-butanediol di(meth)acrylate, (ethoxylated)₂₋₄₀ ethylene glycoldi(meth)acrylate, (propoxylated)₂₋₄₀ ethylene glycol di(meth)acrylate,(ethoxylated)₂₋₄₀ propylene glycol di(meth)acrylate, (propoxylated)₂₋₄₀propylene glycol di(meth)acrylate, (ethoxylated)₂₋₄₀1,4-cyclohexanedimethanol di(meth)acrylate, (propoxylated)₂₋₄₀1,4-cyclohexanedimethanol di(meth)acrylate, (ethoxylated)₂₋₄₀bisphenol-A di(meth)acrylate, (propoxylated)₂₋₄₀ bisphenol-Adi(meth)acrylate, (ethoxylated)₃₋₆₀ glycerol tri(meth)acrylate,(propoxylated)₃₋₆₀ glycerol tri(meth)acrylate, (ethoxylated)₃₋₆₀trimethylolpropane tri(meth)acrylate, (propoxylated)₃₋₆₀trimethylolpropane tri(meth)acrylate, (ethoxylated)₃₋₆₀ isocyanuratetri(meth)acrylate, (ethoxylated)₃₋₆₀ isocyanurate tri(meth)acrylate,(ethoxylated)₄₋₈₀ pentaerythritol tetra(meth)acrylate,(propoxylated)₄₋₈₀ pentaerythritol tetra(meth)acrylate,(ethoxylated)₆₋₁₂₀ dipentaerythritol tetra(meth)acrylate,(propoxylated)₆₋₁₂₀ dipentaerythritol tetra(meth)acrylate.

The polymerizable compound B or mixtures of different polymerizablecompounds B may be used in an amount of 10 to 30 percent by weight,preferably in an amount of 13 to 27 percent by weight, and morepreferably in an amount of 18 to 25 percent by weight, based on thetotal amount of the aqueous-based composition of the present invention.

Component d)—Encapsulated Free Radical Initiator

The aqueous-based composition of the present invention further comprisesat least one encapsulated free radical initiator, wherein said freeradical initiator is encapsulated in the microcapsules. The curing isactivated by rupture of the microcapsules resulting in reaction of thepolymerizable components of the aqueous-based composition with the freeradical initiator, which is released from the microcapsules. By curingof the aqueous-based composition of the present invention the threads ofthe reciprocally threaded article are bonded together. Good bondstrengths, even at high temperatures can be achieved as measured by thetorque required to unlock threaded articles locked to each other byaqueous-based compositions of the invention from each other.

The microcapsule itself is desirably a double walled microcapsule. Anexample of a double walled microcapsule is one including wallsconstructed of gelatin and/or polyoxymethylene urea (PMU).

It has been found that the mean diameter of the microcapsules isdesirably in the range of from 100 μm to about 140 μm though it will beappreciated that individual microcapsules may have a diameter welloutside these mean ranges. For example individual microcapsules can havea diameter in the range of from 50 μm to 200 μm. Suitably the meandiameter is in the range from 110 μm to about 130 μm. Typically the meandiameter will be about 120 μm.

The mean diameter is defined as a 50% limit (D50) in microcapsuledistribution whereby 50% by volume of the microcapsules have a diameterbelow the 50% limit and 50% by volume of the microcapsules have adiameter above the 50% limit.

The mean diameter of the microcapsules can be determined by using aLaser Diffraction Particle Size Analyzer.

The free radical initiator is preferably selected from peroxidecompounds such as cumene hydroperoxide (CHP); tert-butyl peroxybenzoate(TBPB); t-butylhydroperoxide (TBH), methyl ethyl ketone peroxide;benzoyl peroxide; acetyl peroxide;2,5-dimethylhexane-2,5-dihydroperoxide; di-tert-butyl perphthalate;dicumyl peroxide; 2,5-dimethyl-2,5-bis(tert-butylperoxide)hexane;2,5-dimethyl-2,5-bis(tert-butylperoxy)hexyne;bis(tert-butylperoxyisopropyl)benzene; di-t-butyl peroxide;1,1-di(tert-amylperoxy)-cyclohexane;1,1-di-(tert-butylperoxy)-3,3,5-trimethylcyclohexane;1,1-di-(tert-butylperoxy)-cyclohexane; 2-di-(tert-butylperoxy)butane;n-butyl-4,4-di(tert-butylperoxy)valerate;ethyl-3,3-di-(tert-amylperoxy)butyrate;ethyl-3,3-di(tert-butylperoxy)-butyrate; t-butyl peroxy-neodecanoate;di-(4-5-butyl-cyclohexyl)-peroxydicarbonate; lauryl peroxide;2,5-dimethyl-2,5-bis(2-ethyl-hexanoyl peroxy) hexane; p-menthanehydroperoxide; diisopropylbenzene hydroperoxide; pinene hydroperoxide;t-amyl peroxy-2-ethylhexanoate. Additionally, one or more of the freeradical initiators from this list may be combined. A particularpreferred free radical initiator of the present invention is benzoylperoxide.

Non-peroxide free radical initiators may also be employed, such as, forexample, 2,2′-azobis(2-methyl-propionitrile),2,2′-azobis(2,4-methylbutanenitrile), or even in some cases a radiationcure initiator, or co-initiator.

The free radical initiator may promote curing at a temperature of 0° C.to 200° C., preferably at 10° C. to 40° C.

Desirably the concentration of the at least one free radical initiatorwithin the capsule is between 1 and 50%, more typically between 2 to40%, suitably 3 to 30% for example 4 to 20% (weight/weight).

The encapsulated free radical initiator or mixtures of differentencapsulated free radical initiators may be used in an amount of 1 to 8percent by weight, preferably in an amount of 2 to 7 percent by weight,and more preferably in an amount of 3 to 6 percent by weight, based onthe total amount of the aqueous-based composition of the presentinvention.

The aqueous-based composition of the present invention may furthercomprise one or more additives known in the art, including, for example,thickeners, plasticizers, pigments, dyes, accelerators, adhesionpromoters, crosslinking agents, fillers, and flame retardants.

If present, at least one additive or mixtures of different additives maybe used in an amount of 0.1 to 20 percent by weight, preferably in anamount of 1 to 18 percent by weight, and more preferably in an amount of3 to 15 percent by weight, based on the total amount of theaqueous-based composition of the present invention.

In particular it is desirable to include one or more thickeners tothicken the uncured aqueous-based composition which is usually liquid.The thickening of the aqueous-based composition imparts sufficientviscosity to said composition so that it has the physical properties toallow and maintain the dispersion of the other components in thecomposition. In particular it is desirable that the microcapsules remaindispersed throughout the aqueous-based composition. If the aqueous-basedcomposition was not sufficiently viscous the settling out one or morecomponents a) to d) may occur.

Suitable thickeners include, for example, organic thickener materialssuch as waxes and polymeric thickeners and also inorganic thickenermaterials such as silica.

Suitable polymeric thickener materials include polymethyl methacrylate(PMMA); polyethylene materials; fluoropolymers includingpolytetrafluoroethylene (Teflon) materials; nylon materials; and copolymer materials such as methyl/n-butyl methacrylate copolymers. Any ofthe foregoing may be provided in powder form.

Gums such as xanthum gum (also polymeric) may be utilized also.

Silica has been found to be a very useful inorganic thickener materialin accordance with the present invention. It achieves the necessarythickening of the aqueous-based composition without interfering to anysubstantial extent with the curing of the aqueous-based composition.

Suitable silicas, such as fused silicas, may be untreated or treated soas to alter the chemical nature of their surface. Virtually anyreinforcing fused silica may be used.

Particularly desirable silicas have a low ion concentration and arerelatively small in particle size (e.g., on the order of about 12 μm,with a median of up to about 30 μm and as low as less than about 2 μm),such as the Silbond materials, commercially available under thetradename Aerosil 200, supplied by Evonik.

Other materials may be added as inorganic thickener materials andinclude those constructed of or containing aluminum oxide, siliconnitride, aluminum nitride, silica-coated aluminum nitride and micronizedquartz, provided they are not basic in nature.

A further additive suitable for use in the aqueous-based compositions ofthe present invention is a plasticizer. While many plasticizers may beutilized, it is desirable that the plasticizer is a polymeric one. Otherplasticizers may also be included in the inventive composition, examplesof which include those available commercially from Union Carbide, suchas under the trade designations TONE Polyol 301 and 310. Other suitableplasticizers include expandable plastic such as those sold under thetrade name EXPANCEL, which is a registered trade-mark for microspheresthat are small spherical plastic particles. The microspheres consist ofa polymer shell encapsulating a gas. When the gas inside the shell isheated, it increases its pressure and the thermoplastic shell softens,resulting in a dramatic increase in the volume of the microspheres (by afactor of 40). The specific material that can be used is DE 80 or DE 30.

It can be useful to impart a colour to the aqueous-based compositions ofthe present invention, as the colour can be used as a product indicatorin many ways, usually to allow for ease or recognition, for example, toindicate a particular size of bolt or nut, the customer to whom thethreaded article with the pre-applied product should be delivered.

Suitable pigments or dyes include coloured metal complexes for exampleFe and Co complexes. Specific examples include: Rocket Red T-13 (organicpigment based on a thermoset resin matrix including an Fe complexmaterial available from Dayglo Color Corp); also Laser Red 2 and LaserRed 3 with similar chemistry and available from Sterling; Cobaltaluminate complexes such as the product PKSO91 from Ferro B. V. andComet Blue 3 from Swada (both Cobalt aluminate blue spinet materials);V-9248 Blue (Cobalt chromite blue-green spinet from Ferro B. V.); F-5686Turquoise (Cobalt chromite blue-green spinet Co(Al,Cr)2O4:MgO:ZnO from:Ferro B. V.). In general Fe complexes impart a red colour whereas Cocomplexes impart a blue colour.

Suitable accelerators include metallocenes, i.e., those metallocenes ormetallocene containing materials that, in the presence of theaforementioned free radical initiators, effectuate polymerization of thepolymerizable components of the aqueous-based composition.

Metallocenes are typically of three types, i) thedicyclopentadienyl-metals with the general formula (C₅H₅)₂M, ii) thedicyclopentadienyl metal halides of the formula (C₆H₅)₂MX_(s), where Xis a halide, such as Cl or Br, and s is 1, 2 or 3; and iii)monocyclopentadienyl-metal compounds with the general formula C₅H₅MR⁸_(s), where s is as defined above and R⁸ is CO, NO, a halide group, analkyl group, etc., and, in each instance, M is a transition metal,especially copper or iron, most preferably iron. Although themetallocene is preferably employed as the metallocene compound itself,the activator may also be in the form of polymers incorporating themetallocene and the acyl, alkyl, hydroxyalkyl and alkenyl derivatives ofthe metallocenes, preferably such derivatives having from 1 to 18,preferably from 1 to 8, carbon atoms, as well as combinations of any ofthe foregoing.

Suitable metallocenes include ferrocene, n-butyl ferrocene, titanoceneand cupricene. These and other metallocenes and their preparation aredescribed in, e.g., Malofsky—U.S. Pat. No. 3,855,040, Wojciak—U.S. Pat.No. 4,093,556, and Rosenblum et. al.—U.S. Pat. No. 5,124,464. As notedabove, the preferred accelerators are those metallocenes that are basedon iron, especially ferrocene itself, as well as the various derivativesthereof, particularly n-butyl ferrocene.

The metallocene or metallocene based accelerators can be present in anamount of from about 0.001 to about 5 wt %, preferably from about 0.01to about 2 wt %, most preferably from about 0.05 to about 0.1 wt %,based on the total amount of the aqueous-based composition.

The aqueous-based compositions of the present invention may furthercomprise at least one adhesion promoter. The adhesion promoter is anyorganic compound that contains an adhesion promoting group that canassist in the adhesion of the aqueous-based composition or the curedproduct of the aqueous-based composition to a surface, such as a metal.

The adhesion promoting group can be a hydroxide, amine, or mercaptangroup, any of which may be aliphatic, aryl or heteroaryl.

Preferably, the adhesion promoting group is a ketoximine; acetarylamide;hydroxy silane or silicone; aryl or heteroaryl hydroxide (e.g phenolichydroxide); N-containing heterocycle (e.g as imidazole, benzimidazole,triazole, benztriazole, thiazole, isothiazole); acid anhydride;β-diketone, β-keto ester, β-keto aldehyde β-keto heterocycle group; oran acid group (especially carboxylic acid, phosphonic acid and sulphonicacid group).

Preferred adhesion promoters include methacryloxyethyl succinate,methacryloxyethyl maleate and bis (methacryloxyethyl) phosphate, and/orcombinations thereof.

The adhesion promoter or mixtures of different adhesion promoters can bepresent in an amount of from 0.01 to 5 wt %, preferably from 0.1 to 2 wt%, most preferably from 0.4 to 0.8 wt %, based on the total amount ofthe aqueous-based composition.

Crosslink agents suitable for use with the present invention include anyknown crosslinking material provided that the physical and chemicalstability of the aqueous-based composition is substantially unaffectedby inclusion of the crosslinking material. In some embodiments of thepresent invention, the aqueous-based compositions may comprise at leastone crosslinking agent selected from allyl methacrylate (ALMA);divinylbenzene (DVB); 1,3-butanediol dimethacrylate (BGDMA);tripropyleneglycol diacrylate (TRPGDA); trimethylolpropanetrimethacrylate (TMPTMA); trimethylolpropane triacrylate (TMPTA) andcombinations thereof.

The crosslinking agent or mixtures of different crosslinking agents canbe present in an amount of from about 0.01 to about 10 wt %, preferablyfrom about 1 to about 8 wt %, most preferably from about 2 to about 5 wt%, based on the total amount of the aqueous-based composition.

Other additives may also be included in the inventive aqueous-basedcompositions to confer additional physical properties, such as fillers,flame retardants and/or compounds that enhance resistance to thermaldegradation [for instance, maleimide compounds such asN,N′-meta-phenylene bismaleimide (see U.S. Pat. No. 3,988,299)].

In one preferred embodiment of the present invention the aqueous-basedcomposition comprises, based on the total amount of the aqueous-basedcomposition:

-   -   a) from 15 to 40 percent by weight, more typically from 20 to 35        percent by weight, suitably from 25 to 30 percent by weight, for        example from 26 to 29 percent by weight of at least one carboxyl        group containing (co)polymer;    -   b) from 2 to 10 percent by weight, more typically from 3 to 9        percent by weight, suitably from 4 to 8 percent by weight, for        example from 5 to 7 percent by weight of at least one        polymerizable monomer A containing one acryloyl group;    -   c) from 10 to 30 percent by weight, more typically from 13 to 27        percent by weight, suitably from 18 to 25 percent by weight, for        example from 20 to 24 percent by weight of at least one        polymerizable compound B containing at least two acryloyl        groups;    -   d) from 1 to 8 percent by weight, more typically from 2 to 7        percent by weight, suitably from 3 to 6 percent by weight, for        example from 3 to 5 percent by weight of at least one        encapsulated free radical initiator;    -   e) from 10 to 72 percent by weight of water; more typically from        20 to 60 percent by weight, suitably from 25 to 50 percent by        weight, for example from 30 to 40 percent by weight of water;        and    -   f) from 0 to 20 percent by weight, more typically from 0.1 to 20        percent by weight, suitably from 1 to 18 percent by weight, for        example from 3 to 15 percent by weight of one or more additives.

The inventive aqueous-based compositions have desirable properties, suchas forming a dry to touch (tack-free) coating on the surface offasteners, like threaded fasteners. This is important because the coatedfasteners do not stick together or stick to other surfaces, such assupply tubes where they could cause blockages.

In this regard, the invention also provides a coated fastener obtainedby a process, comprising the steps of:

-   -   a) providing a fastener, preferably a threaded fastener;    -   b) applying to at least one part of the fastener an        aqueous-based composition of the present invention;    -   c) drying the fastener at temperatures from 15° C. to 120° C.,        preferably from 20° C. to 90° C. to form a coated fastener.

As employed herein, the term “fastener” refers to any suitablefastening, connecting or tightening mechanism expressly including, butnot limited to, threaded fasteners. Preferred fasteners are selectedfrom bolts, screws, studs, nuts, nails, such as threaded nails, fittingsand the like.

Typically the threads of the fastener engage with reciprocal threads ofa receiver for the fastener for example a threaded bore or nut and thecuring of the inventive composition, which forms a coating on thesurface of the fastener, is activated on screw thread engagement of thefastener to act as a threadlocking composition to lock the threadstogether or as a thread sealant composition to provide a seal about (thethreads of) the fastener. The curing process is activated by rupture ofthe microcapsules resulting in reaction of the polymerizable componentsof the aqueous-based composition with the free radical initiator, whichis released from the microcapsules.

In this regard, the invention also relates to reciprocally threadedarticles having their respective threads bonded together by the curedproduct of the aqueous-based composition of the present invention.

Additionally, the invention relates to a method for sealing andthreadlocking a reciprocally threaded article, steps of which include:

-   -   a) applying to at least one part of a threaded fastener an        aqueous-based composition of the present invention;    -   b) drying the threaded fastener at temperatures from 15° C. to        120° C., preferably from 20° C. to 90° C. to form a coated        fastener;    -   c) engaging the thread of the coated fastener with reciprocal        thread of a receiver to form a reciprocally threaded article,        wherein the threads of the reciprocally threaded article are        bonded together by the cured product of the aqueous-based        composition of the present invention.

A final object of the invention is the use of the aqueous-basedcomposition of the present invention for sealing or coating threadedfasteners and for threadlocking reciprocally threaded articles.

EXAMPLES Example 1

An aqueous-based composition according to the invention was made byusing the following components:

-   -   Carboxyl group containing (co)polymer:        NeoCryl A-1120, an aqueous anionic, acrylic styrene copolymer        dispersion (total solids (55% w/w), commercially available from        DSM Neo Resins.    -   Polymerizable monomer A of the present invention    -   Polymerizable compound B containing at least two acryloyl        groups:        Ethoxylated bisphenol A dimethacrylate (EBIPMA), commercially        available from Sartomer under the tradename SR348L.    -   Encapsulated free radical initiator:        Microencapsulated di-benzoyl peroxide.    -   Accelerator:        N-butyl ferrocene, commercially available from Parish Chemical        Company

The aqueous-based composition additionally comprises further additives,which include at least one adhesion promoter, at least one crosslinkingagent, and at least one compound which enhance the resistance of thecured formulation to thermal degradation.

The components of the aqueous-based composition are given in Table 1 inamounts based on w/w of the composition excluding the encapsulated freeradical initiator. The part of the composition excluding theencapsulated free radical initiator and the encapsulated free radicalinitiator were combined in the following ratio by weight: 97 parts ofthe composition excluding the encapsulated free radical initiator to 3parts encapsulated free radical initiator.

TABLE 1 Percent weight of components in the part of the aqueous-basedcomposition excluding the encapsulated free radical initiator Component% weight NeoCryl A-1120 58.00 Polymerizable monomer A 6.30 EBIPMA 22.73N-butyl ferrocene 0.06 Additives 12.91 Total 100

The aqueous-based composition is prepared by adding the ingredients inthe order shown using high speed mixing.

To demonstrate the effect of the polymerizable monomer A, a comparativeformulation was prepared which does not comprise a polymerizable monomerA of the present invention.

Example 2 Application of the Aqueous-Based Composition

The aqueous-based composition of Example 1 was applied to M10×50threaded steel bolt specimens. All specimens were dried for 0.5 h at 70°C. to 85° C.

When using the aqueous-based composition of Example 1 a dry to touch(tack-free) coating was formed on the surface of the specimens, whereasa tacky coating was obtained, when using the aforementioned comparativeformulation which does not comprise a polymerizable monomer A of thepresent invention.

In accordance with ASTM D5649, the coated bolts were assembled withclean matching steel nuts engaging the coated product completely.Breakaway and Prevail (after 180° rotation) strengths were measuredafter (a) 24 hr cure at 22° C.; (b) 24 hr cure at 22° C. followed by 2hrs at 150° C., measured at 150° C.; (c) 24 hr cure at 22° C. followedby 2 hrs at 200° C., measured at 200° C.; and (d) 24 hr cure at 22° C.followed by 2 hrs at 250° C., measured at 250° C. Results are shown inTable 2:

TABLE 2 Strength Performance on M10 bolts Conditions Break strength 24hr cure at 22° C. 23 Nm 150° C. hot strength 13 Nm 200° C. hot strength12 Nm 250° C. hot strength 15 Nm Conditions Prevail strength 24 hr cureat 22° C. 13 Nm 150° C. hot strength 10 Nm 200° C. hot strength 12 Nm250° C. hot strength  7 Nm

I claim:
 1. A coated fastener obtained by a process, comprising thesteps of: a) providing a fastener, preferably a threaded fastener; b)applying to at least one part of the fastener an aqueous-basedcomposition comprising: i) at least one carboxyl group containing(co)polymer; ii) at least one polymerizable monomer A containing oneacryloyl group; iii) at least one polymerizable compound B containing atleast two acryloyl groups; iv) at least one encapsulated free radicalinitiator; and v) water; and c) drying the fastener at temperatures from15° C. to 120° C. to form a coated fastener.
 2. Reciprocally threadedarticles having their respective threads bonded together by the curedproduct of an aqueous-based composition having been comprised of: i) atleast one carboxyl group containing (co)polymer; ii) at least onepolymerizable monomer A containing one acryloyl group; iii) at least onepolymerizable compound B containing at least two acryloyl groups; iv) atleast one encapsulated free radical initiator; and v) water.
 3. A methodfor sealing and threadlocking a reciprocally threaded article, steps ofwhich include: a) applying to at least one part of a threaded fasteneran aqueous-based composition comprising: i) at least one carboxyl groupcontaining (co)polymer; ii) at least one polymerizable monomer Acontaining one acryloyl group; iii) at least one polymerizable compoundB containing at least two acryloyl groups; iv) at least one encapsulatedfree radical initiator; and v) water; b) drying the threaded fastener attemperatures from 15° C. to 120° C. to form a coated fastener; c)engaging the thread of the coated fastener with reciprocal thread of areceiver to form a reciprocally threaded article, wherein the threads ofthe reciprocally threaded article are bonded together by the curedproduct of the aqueous-based composition.
 4. A process of using anaqueous-based composition for sealing or coating threaded fasteners orfor threadlocking reciprocally threaded articles, steps of whichcomprise: a) providing unassembled threaded fasteners; and b) providingto thread of the unassembled threaded fasteners an aqueous-basedcomposition comprising: i) at least one carboxyl group containing(co)polymer; ii) at least one polymerizable monomer A containing oneacryloyl group; iii) at least one polymerizable compound B containing atleast two acryloyl groups, to form a threaded fasteners assembly; iv) atleast one encapsulated free radical initiator; and v) water; and c)exposing the threaded fasteners to conditions favorable to cure theaqueous-based composition.